I have the Metabones adaptor for my Contax G lenses. It works fine with my 45 and 90mm lenses, and they perform superbly. Takes a bit of getting used to. The adaptor is superbly made, but must be fitted quite carefully to the lens and then the whole mounted to the body - I have used then on a GH1 and a GF1. The focus can be a bit gritty at first - the metal ring is turning a small, geared screw that fits into the slotted focus drive shaft of the lens. It does loosen up ok. The Metabones is expensive, but I think you need that quality of engineering to have these lenses function reasonably well on M43.